With the economic and social development and the population growth, domestic and industrial water consumption correspondingly increased. The statistical report of the Ministry of Environmental Protection shows that city sewage discharge amount in China is up to a total 71.62 billion tons in 2015, together with worsening water pollution, and many cities and districts have faced water resource crisis. The city sewage contains only 1% of pollutants and has merits such as nearby available, amount stable, easy collection, etc. So, reuse of municipal wastewater is the first choice to solve the problem of water shortage in all over the world. At present, aerobic biological treatment is the main method used in city sewage treatment, which needs large energy consumption. Therefore, it is necessary to search for other alternative techniques in order to reduce the energy consumption.
Forward osmosis membrane separation technique (forward osmosis, FO) has become a research hotspot in wastewater treatment and reuse due to its own unique advantages. In FO process, water passes through a semi-permeable membrane from lower to higher salt concentration side while solute molecules or ions are rejected. The driving force is actually a difference in chemical potential because the lower the concentration, the higher the water chemical potential. Since there is no need to apply pressure, so that the desired power consumption is low. In addition, FO also has advantages of good effluent-quality and low membrane fouling. However, the remaining concentrates from the feed side of FO and the energy stored in organic contaminants are not recovered.
A microbial fuel cell (MFC) is a bio-electrochemical system that drives an electric current by using bacteria and mimicking bacterial interactions found in nature. It has great potential in wastewater treatment. However, the main obstacle in MFC for wastewater treatment is that the effluent-quality is poor and fails in reaching discharge or reuse standards directly.